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.. . Mysterious "Swarm" of Quakes Strikes Oregon Water _____________________________ |
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. 16 Apr 08 - This weekend scientists will try to puzzle out the cause of a "swarm" of earthquakes that has shaken the seafloor near Oregon in recent weeks. About 600 earthquakes have been recorded in a small region about 190 nautical miles (350 kilometers) offshore from Yachats. Although most of the temblors were small, about magnitude 2 or 3, a few were magnitude 4 or 5. Earthquake swarms normally indicate volcanic activity. But they could represent stresses being released in an unusual manner in the middle section of the Juan de Fuca plate. The scientists say they may find lava oozing out onto the seafloor or hot water percolating up from magma-heated undersea hot springs. They could also come across colder water squeezed out of the underlying crust by tectonic forces. (I’m not sure how this could happen.) All of this, the scientists say, is an example of how much we still have to learn about ocean tectonics. To begin with, said Robert Embley of NOAA's Pacific Marine Environment Laboratory, the area isn't even well mapped. "We don't really know what the topography looks like out there," he said. "Our good maps are just along the plate boundary, where 98 percent of the [normal] seismic activity occurs." And we wonder why our oceans are heating. "Elsewhere, the ocean floor is basically
unmonitored," Embley said.
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